diagnostic and laboratory test

8/6/2019 Diagnostic and Laboratory Test

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Pregnancy can occur anytime after afemale begins menstruating (menarche)

until she reaches menopause. However,most pregnancies occur in women ages15 to 40 years. Pregnancies before theage of 15 and after the age of 35 have anincreased risk of complications.



Indication Of A Pregnancy

The first indication of a pregnancy usuallyis a missed menstrual period.

Laboratory tests or home pregnancy testkits check for human chorionicgonadotropin (hCG) in the woman¶s serumor urine; hCG is a hormone produced bythe placenta



Diagnosis

Hist ory: A complete medical history shouldbe obtained, including :

Medical conditionsMedication use (prescription,supplements);

DietUse of alcohol, tobacco, and illicit drugs;



Many women miss a menstrual periodbefore they suspect pregnancy. Early

symptoms may include tender, swollenbreasts, nausea, vomiting, frequenturination, and fatigue.



At 10 to 12 weeks, fetal heart tones can beheard through a special stethoscope.

The uterus may be palpable low in theabdomen by 12 weeks.



T e sts : Pregnancy can be confirmedthrough laboratory tests or home test kitsthat check for hCG in serum or urine.

Home pregnancy test kits can detect hcgin urine and become positive 9 to 12 daysafter conception



hCG can be detected in the serum in 5%of pregnant women 5 days after conception and in over 98% of pregnantwomen by 11 days after conception.Serum hCG tests have a low false positiverate of 0.01% to 2%.



A false positive test is caused bysubstances in the woman¶s body such asantibodies, rheumatoid factor, or proteinsthat interfere with the test.

� F alse negative tests usually occur withurine samples and usually are due tointerference from medications, dilute urinesamples, or errors in following testingdirections.



Antibody testing looks for syphilis andrubella (German measles) antibodies andblood group and Rh typing identifies bloodgroup antigens



Individuals at risk for diabetes receive aglucose tolerance test.

Additional tests may be done to screen for hepatitis B, toxoplasmosis, and HIV.Cervical cultures may be done to rule outinfection.



� F ew studies have been able to prove thatultrasound is absolutely necessary, but ithas produced two positive results: fewer pregnancies go past their due dates, andwomen carrying fetuses with anomaliescan make decisions about termination

earlier in the pregnancy.



Ultrasound can be done at any time, but itis most useful during the second trimester between weeks 18 and 20; a secondultrasound can be done at 23 to 28 weeks.



Prenatal diagnosis of congenital malformations

and genetic disorders



Prenatal diagnosis of congenitalmalformations and genetic disorders hasincreased with the development of accurate testing methods



Testing is often recommended for womenwho:

1) Are age 35 or older;2) Have a history of parental consanguinity ;



3) Have a personal or parental history of achild with a chromosomal abnormality(e.G., Down syndrome, male relatives withduchenne muscular dystrophy , severehemophilia);

4) Have experienced recurrent miscarriages;



5) Has type 1 diabetes mellitus, epilepsy, or myotonic dystrophy ;

6) has been exposed to certain medications,environmental hazards, or viral infections(e.g., rubella, cytomegalovirus).



Alpha-fetoprotein (A F P)AF P is a protein made by the fetus¶s liver.

If the fetus's spinal cord has not developedcorrectly, increased amounts of A F P mayleak into the mother's bloodstream.



Measurement of alpha-fetoprotein (A F P)levels in maternal blood serum screens for neural tube defects such as absence of allor part of the brain (anencephaly) andprotrusion of part of the spinal cordthrough a gap in the spinal column which

usually results in loss of voluntarymovement in the lower body (spina bifida).



Elevated levels of A F P in the maternalbloodstream can also occur withgestational diabetes, twins, intrauterinegrowth retardation, increased gestationalage, and in pregnancies complicated by

bleedingLow levels of A F P in the mother¶sbloodstream may suggest the presence of

chromosomal abnormalities such as Downsyndrome.



Testing is most sensitive at a gestationalage of 16 to18 weeks but can beperformed anywhere between 15 and 22weeks of gestation.At 15 to 20 weeks, maternal serum levelsof AF P, hCG, and estriol can bemeasured.



A naly sis of the amn io tic flu id (amn iocen te sis)

Analysis of the amniotic fluid(amniocentesis) that surrounds thedeveloping fetus, is used to detect fetalgenetic abnormalities in pregnant womenover age 35 or in those whose familyhistory puts them at high risk for certaingenetic defects



It is usually performed between weeks 14and 20 of the pregnancy.

Under ultrasound guidance, a long needleis passed through the mother¶s lower abdomen into the uterus, and a smallamount of fluid is withdrawn.



The fetal cells that have been shed intothe fluid are analyzed for chromosomalproblems (e.g., Down syndrome), and thefluid is analyzed for abnormally high levelof AF P.



Later in the pregnancy the test candetermine the maturity of the fetus's lungsor if there is Rh incompatibility betweenfetus and mother.The procedure carries an increased risk of miscarriage and maternal Rh sensitization.



The primary advantage of chorionic villussampling is that the procedure can beperformed at 10 to 12 weeks gestation,whereas amniocentesis is performed at 14to 20 weeks gestation.The risk of miscarriage with chorionic villussampling is 2% to 3% higher than for amniocentesis. There is also a small riskof injury to the developing fetus¶ limbs.



Percu taneou s umb ilical cor d s ampl ingCalled also cor d ocen te sis.

Sampling is used after 16 weeks gestationfor rapid chromosome analysis as well asevaluation of fetal metabolism and fetalblood abnormalitiessampling carries risksfor both mother and fetus.



Guided by images on ultrasound, a doctor inserts a needle into the mother¶sabdomen and withdraws a sample of thebaby¶s blood from the umbilical cord.Because this is an invasive procedure,percutaneous umbilical cord



If the mother is of African origin, a testfor sickle cell anemia may be ordered.

� Jewish mothers of eastern Europeanancestry (Ashkenazi J ews) and F rench

Canadians should be tested for the Tay-Sachs gene.

diagnostic and laboratory test

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